Structural wooden joist

ABSTRACT

The structural wooden joist described comprises an elongated lower chord, an elongated upper chord and an openwork web structure joining the chords and consisting of a series of connector members formed of inclined branches and adhesively secured to the lower and upper chords. Each branch of a connector member is formed of at least two planks having contiguous sides adhesively joined to one another. The connector members define a series of triangular openings in the web structure.

FIELD OF THE INVENTION

[0001] The present invention pertains to a structural wooden joist used in building constructions.

BACKGROUND OF THE INVENTION

[0002] Wooden joists are used increasingly in a number of building applications. They comprise top and bottom elongated chords with intervening struts joined to the chords by means of scarfing.

[0003] One such wooden joist may be found described in U.S. Pat. No. 5,664,393 issued to Applicant on Sep. 9, 1997 and consists of lower and upper chords which are joined by an openwork web structure. This web structure includes, between opposite ends thereof, a series of horizontally-spaced trapezoidal laminated panels defining of series of triangular spacing therebetween. Each panel has opposite short and long sides adhesively joined to the lower and upper chords respectively, and each panel is formed of short obliquely extending planks adhesively secured edgewise to one another.

[0004] It has been found that such structure does not offer adequate resistance to humidity variations which cause some deformation of the joist structure.

OBJECTS AND STATEMENT OF THE INVENTION

[0005] It is an object of the present invention to provide an improved wooden joist which overcomes the above-mentioned problem known in the prior art. The joist is characterized by an openwork web structure joined to the chords wherein the web structure consists of a series of connector members formed of inclined branches, each branch being formed of at least two adhesively secured planks. The present invention therefore relates to a structural wooden joist which comprises:

[0006] a) an elongated lower chord;

[0007] b) an elongated upper chord in a spaced apart generally parallel opposed relation to the lower chord; and

[0008] c) an openwork web structure joining the chords; this web structure comprising a series of connector members formed of inclined branches and adhesively secured to the lower and upper chords; each branch of the connector members being formed of at least two planks having contiguous sides adhesively joined to one another; the connector members defining a series of triangular openings in the web structure.

[0009] In one form of the invention, each opposite end of the web structure includes a laminated panel which is formed of a series of planks secured edgewise to one another and having their upper and lower sides adhesively joined to the upper and lower chords.

[0010] In another form of the invention, the obliqueness of the branches of the connector members has a different angle relative to the horizontal plane of the chords depending on the height of the joist.

[0011] Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that this detailed description while indicating preferred embodiments of the invention, is given by way of illustration only since various changes and modifications within the spirit and scope of the invention will be come apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an elevational view of a wooden joist made in accordance with the present invention;

[0013]FIG. 2 shows a V-shaped arrangement of two connector members;

[0014]FIG. 3 is an end view of the arrangement shown in FIG. 2;

[0015]FIG. 4 is an elevational view of one end section of the panel structure joined to a connector member;

[0016]FIG. 5 is an elevational view of another embodiment of a wooden joist made in accordance with the present invention; and

[0017]FIG. 6 is another embodiment of a V-shaped arrangement of two connector members.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] Referring to FIG. 1, there is shown a structural wooden joist, generally denoted 10, which comprises an elongated lower chord 12 and an elongated upper chord 14 spaced apart generally in opposed relation to the lower chord.

[0019] An openwork web structure is displayed between the chords 12 and 14. In a major portion of the web structure, there is shown two arrangements of connector members 16, which extend diagonally between the upper and lower chords 12 and 14. These obliquely extending connector members 16 define a series of triangular-shaped openings 18 allowing for passage of various building utilities, such as electrical wires, water conduits, air ducts and like.

[0020] Referring to FIGS. 2 and 3, there is shown a V-shaped arrangement of two contiguous connector members 16 a, 16 b, each consisting of a pair of planks 24, 26 (for connector 16 a) and 28, 30 (for connector 16 b). Planks 24 and 26 are secured to one another along their contiguous side 32, while planks 28 and 30 are secured to one another along their contiguous side 34. The planks are preferably glued together. The opposite ends of the planks 24, 26, 28 and 30 are scarfed. The scarf joints 24 a, 26 a, 28 a and 30 a are adhesively secured to the upper chord 14 while the lower extremities 26 b and 30 b of the planks are also scarfed and adhesively secured to the lower chord 12.

[0021] At each opposite end of the joist, the web structure includes laminated panels 36 and 38. Referring to FIG. 4, the laminated panel 38 is formed of a series of vertically extending planks 40 which are secured to one another in edgewise manner, the planks having scarfed joints 40 a and 40 b, which are adhesively connected to the upper and lower chords. The innermost plank 40′ of the laminated panel is joined to a connector member 16 by means of a scarfed edge 41 joined to the scarfed edge 43 of plank 28. A structural glue may also be used to further secure the panels to the chords.

[0022] Referring to FIGS. 5 and 6, there is shown another embodiment 110 of the present invention wherein the connector members 116 are adhesively secured to the lower chord 112 and upper chord 114. In this joint, the web structure has no central region free of connectors such as shown in FIG. 1, the connector members defining a continuous inclined branch arrangement between the two end panels 136 and 138. As illustrated in FIG. 6, each connector member 116 a, 116 b is formed of two obliquely extending planks 124, 126 and 128, 130 having different width. These planks are joined to one another along their contiguous sides 132, 134 as well as to the upper/lower chords in manner similar to that described above with respect to the connector member 16 illustrated in FIG. 2.

[0023] The inclination given to the connector member 16 of FIGS. 1-4 and 116 of FIGS. 5 and 6 depends on the height of the joist. For example, for the joist shown in FIGS. 1-4, having a height H₁ of about 9.25 inches, for example, the angle a between the planks and the chord is about 35°. On the other hand, for the joist of FIGS. 5 and 6 having a height H₂ of about 11.25 inches, for example, the angle a is about 42°.

[0024] The wood used for all planks of the panel is a kiln dry wood, preferably one selected from the group consisting of fir, spruce and pine. The wood fibers extend in the longitudinal direction of the planks.

[0025] Also, the structural glue used in securing the planks together as well as used in the scarfing, is one preferably having a base of resin resorcinol such as phenol-resorcinol resin, or one having a base of urethane, or any one approved for structural wood construction.

[0026] Although the invention has been described above in respect to specific forms, it will be evident to a person skilled in the art that it may be modified and refined in various ways. For example, although a pair of planks has been illustrated for each branch, the latter could also be formed of more than two planks. Additionally, a single plank could be formed of two superposed planks joined by finger joints and glue. It is therefore wished to have it understood that the present invention should not be limited in scope except by the terms of the following claims. 

1. A structural wooden joist comprising: a) an elongated lower chord; b) an elongated upper chord in a spaced apart generally parallel opposed relation to said lower chord; and c) an openwork web structure joining said chords; said web structure comprising a series of connector members formed of inclined branches and adhesively secured to said lower and upper chords; each said branch of said connector members being formed of at least two planks having contiguous sides adhesively joined to one another; said connector members defining a series of triangular openings in said web structure.
 2. A structural wooden joist as defined in claim 1, wherein each said opposite ends of said web structure displays a laminated panel; each said laminated panel being formed of a series of elongated vertical planks secured edgewise to one another and having upper and lower sides thereof adhesively joined to said upper and lower chords.
 3. A structural wooden joist as defined in claim 2, wherein each said connector member at each opposite end of said web structure is adhesively joined to a chord member and to an innermost plank of said laminated panel.
 4. A structural wooden joist as defined in claim 1, wherein said connector members of said web structure have upper and lower edges secured to said chords by finger joints.
 5. A structural wooden joist as defined in claim 2, wherein said planks of said connector members and of said laminated panels are glued edgewise to one another.
 6. A wooden structural joist as defined in claim 1, wherein said web structure further includes a central region free of connector members.
 7. A structural wooden joist as defined in claim 6, further comprising a laminated panel structure in said central region; said panel structure defining an uninterrupted surface having opposite lower and upper sides adhesively joined to said lower and upper chords respectively; said panel structure of said central region being formed of a series of vertical planks secured edgewise to one another.
 8. A structural wooden joist as defined in claim 7, wherein said planks are glued edgewise to one another.
 9. A structural wooden joist as defined in claim 1, wherein said planks are made of kiln dry wood.
 10. A structural wooden joist as defined in claim 9, wherein said wood is selected from the group including fir, spruce and pine.
 11. A structural wooden joist as defined in claim 1, wherein fibres in said planks extend in the longitudinal direction of said planks.
 12. A structural wooden joist as defined in claim 1, wherein each branch of said connector member extends obliquely at about 35° relative to said chords for a joist having a height of about 9.25 inches.
 13. A structural wooden joist as defined in claim 1, wherein each branch of said connector member extends obliquely at about 42° relative to said chords for a joist having a height of about 11.25 inches. 